Apparatus for an optimized plasma chamber grounded electrode assembly

ABSTRACT

An electrode assembly configured to provide a ground path for a plasma processing chamber of a plasma processing system is disclosed. The apparatus includes an electrode configured to be exposed to a plasma. The apparatus also includes a heater plate disposed above the electrode, wherein the heater plate is configured to heat the electrode. The apparatus further includes a cooling plate disposed above the heater plate, wherein the cooling plate is configured to cool the electrode. The apparatus also includes a plasma chamber lid configured to confine the plasma in the plasma chamber, wherein the plasma chamber lid includes a ground. The apparatus further includes a clamp ring configured to secure the electrode, the heater plate, and the cooling plate to the plasma chamber lid, the clamp ring is further configured to provide the ground path from the electrode to the chamber lid.

BACKGROUND OF THE INVENTION

The present invention relates in general to substrate manufacturingtechnologies and in particular to an apparatus for an optimized plasmachamber electrode assembly.

In the processing of a substrate, e.g., a semiconductor substrate or aglass panel such as one used in flat panel display manufacturing, plasmais often employed. As part of the processing of a substrate for example,the substrate is divided into a plurality of dies, or rectangular areas,each of which will become an integrated circuit. The substrate is thenprocessed in a series of steps in which materials are selectivelyremoved (etching) and deposited. Control of the transistor gate criticaldimension (CD) on the order of a few nanometers is a top priority, aseach nanometer deviation from the target gate length may translatedirectly into the operational speed and or operability of these devices.

In an exemplary plasma process, a substrate is coated with a thin filmof hardened emulsion (such as a photoresist mask) prior to etching.Areas of the hardened emulsion are then selectively removed, causingparts of the underlying layer to become exposed. The substrate is thenplaced in a plasma processing chamber on a substrate support structurecalled a chuck (e.g., mono-polar, bi-polar electrode, mechanical, etc.).An appropriate set of plasma gases is then flowed into the chamber andstruck to form a plasma to etch exposed areas of the substrate with aparticular topography.

Referring now to FIG. 1, a simplified diagram of a capacitive coupledplasma processing system is shown. In general, a plasma is sustainedbetween a grounded electrode 106 and a powered lower electrode (chuck)105. A first RF generator 134 generates the plasma as well as controlsthe plasma density, while a second RF generator 138 generates bias RF,commonly used to control the DC bias and the ion bombardment energy.

Further coupled to source RF generator 134 and bias RF generator 138 ismatching network 136 that attempts to match the impedances of the RFpower sources to that of plasma 110. Furthermore, pump 111 is commonlyused to evacuate the ambient atmosphere from plasma chamber 102 in orderto achieve the required pressure to sustain plasma 110. In addition,plasma 110 may be confined between chuck 105 and grounded electrode 106by means of confinement rings 103, which may control a pressure withinplasma 110. Confinement rings 103 can be moved to increase and decreasea spacing or gap between adjacent confinement rings, commonly by the useof cam ring. Gas distribution system 122 is commonly comprised ofcompressed gas cylinders containing plasma processing gases (e.g., C₄F₈,C₄F₆, CHF₃, CH₂F₃, CF₄, HBr, CH₃F, C₂F₄, N₂, O₂, Ar, Xe, He, H₂, NH₃,SF₆, BCl₃, Cl₂, WF₆, etc).

In general, in order to achieve a substantially uniform enchant gasdistribution across the surface of a substrate, the grounded electrodetypically includes perforations or pores, in a showerhead configuration,through which the plasma gases may pass into the plasma chamber. In acommon configuration, an electrode assembly usually includes the chamberlid (in order to securely attach the electrode components in the plasmachamber), a cooling plate and a heating plate (in order to preventplasma gas reactions from taking place within the perforations orpores), a backing plate (in order to electrically isolate the electrodefrom the heating plate and cooling plate, while still allowing a thermalpath between the heating plate and cooling plate and the groundedelectrode), and the grounded electrode itself (in order to distributethe plasma gas across the surface of the substrate, as well as toprovide a rf return ground path for the powered electrode).

Referring now to FIG. 2, a simplified diagram of a common electrodeassembly configuration is shown. Chamber lid 212 is generally configuredto mate with the plasma chamber in order to maintain a substantialvacuum for plasma processing. In general, chamber lid 212 comprises atop plate 212 b and circular stub 212 a that protrudes into the plasmachamber (not shown) and provides a planar surface to which a coolingplate 208 or heating plate 206 may be attached. Circular stub 212 a isfurther surrounded by a groove (defined by circular stub 212 a and topplate 212 b) into which gasket 214 is commonly placed. In oneconfiguration, an electrode sub-assembly (including in sequence acooling plate 208, a heating plate 206, a backing plate 204, andgrounded electrode 202) is assembled or sandwiched in a unitaryconstruction, with a first set of metal fasteners, and then attached asa unit to circular stub 212 a with a second set of metal fasteners, inorder to assemble the electrode assembly.

Cooling plate 208 may be cooled by a chiller system that re-circulatesfluid through cavities in within cooling plate 208. In addition, thefluid can be a liquid (e.g., water, etc.) or a gas (e.g., air, etc.).The liquid or air can be chilled for greater cooling effect and can bere-circulated for greater efficiency. This fluid is, in turn, commonlypumped through a set of conduits to an external source of heatconvection, such as a heat exchanger, and returned back to the chuck.Heating plate 206 generally includes a set of resistive elements thatoutput thermal energy to when the set of elements is supplied withelectrical current. In combination with cooling plate 208, heating plate206 allows the plasma gas temperature to be sustained within recipeparameters in order to generally maintain etch quality and substrateyield. Backing plate 204 is commonly made of graphite, backing plategenerally provides temperature uniformity across grounded electrode 202.

However, backing plate 204 is generally made of a material that isrelatively soft (e.g., graphite, etc.). Consequently, helicoil insertsare often required in order to properly mate with threaded metalfasteners. A helicoil is generally an internal thread insert forcreating stronger threads in any assembly prone to thread damage.However, the use of different materials with differing thermal expansionrates may cause defects to form in the electrode assembly as it isrepeatedly heated and cooled. The coefficient of thermal expansion (α)is generally defined as the fractional increase in length per unit risein temperature. The exact definition varies, depending on whether it isspecified at a precise temperature (true α) or over a temperature ranges(mean α). The former may be related to the slope of the tangent to thelength—temperature plot, while the latter may be governed by the slopeof the chord between two points on this curve.

In general, the metal portions of the electrode assembly (e.g., coolingplate 208, heater plate 206, threaded bolts, etc.) generally have ahigher α than the non-metal portions of the electrode assembly (e.g.,backing plate, etc.). For example, aluminum (commonly used in coolingplate 208, heating plate 206, grounded electrode 202, metal fasteners,etc.) generally has a relatively large α (e.g., 23.1×10⁻⁶ K⁻¹), incomparison to graphite (commonly used in backing plate 204) with asmaller α (e.g., 6.5×10⁻⁶ K⁻¹). That is, per a unit increase intemperature, aluminum may expand up to four times as much as graphite.However, the electrode assembly is assembled in a unitary constructionwith metal fasteners that extend through the various components (e.g.,cooling plate, heater plate, backing plate, grounded electrode, etc.),and thus has minimal lateral and longitudinal play between thecomponents. Consequently, repetitive cycling of temperature may stressand hence damage the backing plate 204, and consequently producegraphite particles that may contaminate the plasma chamber. In general,the lateral axis is parallel to the substrate surface, whereas thelongitudinal axis is perpendicular to the substrate surface.

In addition, the use of metal fasteners in the electrode sub-assemblymay also increase the likelihood of arcing. An arc is generally a highpower density short circuit which has the effect of a miniatureexplosion. When arcs occur on or near the surfaces of the targetmaterial or chamber fixtures, substantial damage can occur, such aslocal melting. Plasma arcs are generally caused by low plasma impedancewhich results in a steadily increasing current flow. If the resistanceis low enough, the current will increase indefinitely (limited only bythe power supply and impedance), creating a short circuit in which allenergy transfer takes place. This may result in damage to the substrateas well as the plasma chamber. For example, as the rf electrical chargeis drained away from the powered electrode toward the groundedelectrode, a secondary electrical discharge may occur with a metalfastener, particularly across a perforation or pore.

Furthermore, the large number of metal fasteners also makes assembling,aligning, replacing, and/or installing the electrode sub-assemblycomponents problematic. For example, fastener tolerances may berelatively tight (e.g. 1/1000^(th) inch, etc.). However, after theelectrode assembly has been repeatedly exposed to plasma and/ortemperature cycling, the actual tolerance may have been reduced(tolerance shrinkage). For example, contaminants may have wedgedthemselves into the helicoil, or the fastener holes may have decreasedin size, etc. Consequently, the electrode assembly may be difficult toremove in a safe manner, without damage occurring to the electrodeassembly itself, and without the use of multiple tools (e.g.,screwdriver, hammer, wedge, etc.). For example, graphite is a relativelybrittle material. However, if a hammer needs to be used to dislodge thecooling plate or heating plate from the backing plate, substantialdamage may occur to the graphite.

In addition, since most common electrode assembly configurations do notgenerally include a dedicated rf return path, the electricalcharacteristics of ground may change between successive substrates oralternate recipes, depending on electrode assembly wear, or theelectrical characteristics of the plasma gases used. Generally, mostmaterials used in the electrode assembly are electrically conductive.However, the exact return path to ground may physically shift, and hencemay affect the electrical load on the plasma. For a given processrecipe, it is generally beneficial for the rf power delivery to remainstable throughout the plasma process in order to obtain a reliableprocess result.

In view of the foregoing, there are desired methods and apparatus for anoptimized plasma chamber electrode assembly.

SUMMARY OF THE INVENTION

The invention relates, in one embodiment, to an electrode assemblyconfigured to provide a ground path for a plasma processing chamber of aplasma processing system. The apparatus includes an electrode configuredto be exposed to a plasma. The apparatus also includes a heater platedisposed above the electrode, wherein the heater plate is configured toheat the electrode. The apparatus further includes a cooling platedisposed above the heater plate, wherein the cooling plate is configuredto cool the electrode. The apparatus also includes a plasma chamber lidconfigured to confine the plasma in the plasma chamber, wherein theplasma chamber lid includes a ground. The apparatus further includes aclamp ring configured to secure the electrode, the heater plate, and thecooling plate to the plasma chamber lid, the clamp ring is furtherconfigured to provide the ground path from the electrode to the chamberlid.

The invention relates, in one embodiment, to an electrode assemblyconfigured to provide a ground path for a plasma processing chamber of aplasma processing system. The apparatus includes an electrode configuredto be exposed to a plasma. The apparatus also includes a plasma chamberlid configured to confine the plasma in the plasma chamber, wherein theplasma chamber lid includes a ground. The apparatus further includes aclamp ring configured to secure the electrode to the plasma chamber lid,the clamp ring is further configured to provide the ground path from theelectrode to the chamber lid.

The invention relates, in one embodiment, to an electrode assemblyconfigured to provide a ground path for a plasma processing chamber of aplasma processing system. The apparatus includes an electrode configuredto be exposed to a plasma. The apparatus also includes a plasma chamberlid configured to confine the plasma in the plasma chamber, wherein theplasma chamber lid is configured to form a basket with the electrode andis further configured provide a ground path.

These and other features of the present invention will be described inmore detail below in the detailed description of the invention and inconjunction with the following figures.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is illustrated by way of example, and not by wayof limitation, in the figures of the accompanying drawings and in whichlike reference numerals refer to similar elements and in which:

FIG. 1 shows a simplified diagram of a capacitive coupled plasmaprocessing system;

FIG. 2 shows a simplified diagram of a commonly used electrode assembly;

FIGS. 3A-D show a set of simplified diagrams of an electrode assemblywith a clamp ring, according to an embodiment of the invention; and

FIGS. 4A-C show a set of simplified diagrams of an electrode assembly inwhich a clamp ring is integrated into the chamber lid, according to anembodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will now be described in detail with reference toa few preferred embodiments thereof as illustrated in the accompanyingdrawings. In the following description, numerous specific details areset forth in order to provide a thorough understanding of the presentinvention. It will be apparent, however, to one skilled in the art, thatthe present invention may be practiced without some or all of thesespecific details. In other instances, well known process steps and/orstructures have not been described in detail in order to notunnecessarily obscure the present invention.

While not wishing to be bound by theory, it is believed by the inventorherein that an optimized electrode assembly (e.g., electrode, coolingplate, heater plate, backing plate, etc.) configured with a clamp ringmay provide a consistent rf return path, may be simpler and less timeconsuming to install and remove in a plasma chamber, and maysubstantially reduce particle generation caused by thermal expansion. Inthe discussions that follow, the term “tighten” is employed herein todiscuss moving a fastener into a securing structure. Furthermore, theterm fastener should be understood to apply to a broad range of securingdevices such as such as screws, bolts, clips, and pins.

As previously discussed, in order to achieve a substantially uniformenchant gas distribution across the surface of a substrate, an electrodeassembly (e.g., powered electrode, grounded electrode, etc.) generallyhas perforations or pores (e.g., showerhead). The use of differentmaterials with differing expansion rates may consequently cause defectsto form in the electrode assembly as it is repeatedly heated and cooled.However, in an advantageous manner, the current invention allows theelectrode sub-assembly components (e.g., cooling plate, heater plate,backing plate, electrode, etc.) to be positioned in a pocket formed by aclamp ring without requiring the use of metal fasteners. This pocketconstruction may allow a greater amount lateral and longitudinal playthan in most commonly used configurations, and hence produce lesscontaminants. That is, repetitive cycling of temperature may producesubstantially less stress and hence less damage to the backing plate,and thus minimize the amount of contaminants (e.g., graphite particles,etc.) that are produced. For example, in an embodiment, a lateraltolerance of 1 mm, between electrode assembly components and the innersurface of the clamp ring, may be sufficient to reduce stress. In anembodiment, a longitudinal tolerance of 1 mm, between electrode assemblycomponents and the lateral surface of the electrode away from theplasma, may be sufficient to reduce stress.

In an embodiment, the clamp ring, including the electrode sub-assemblycomponents positioned in the pocket, may be secured to the chamber lid.In general, securing the clamp ring to the chamber lid compresses theelectrode sub-assembly components together for plasma chamber operation.In addition, the clamp ring may be secured to the chamber lid with a setof fasteners that are sufficiently tightened or torqued to compress theelectrode sub-assembly components together. In an embodiment, thefasteners are counter sunk or rounded off in order to reduce arcing, ifdesired. In an embodiment, the clamp ring is secured to the chamber lidwith a set of non-metal fasteners (e.g., ceramic, etc.). In anembodiment, the clamp ring itself is formed into the chamber lid, andhence does not also require metal fasteners. In an embodiment, clampring/chamber lid may be tiered or stepped to secure electrodesub-assembly components.

Furthermore, as the number of fasteners that previously sandwiched theelectrode subassembly (e.g., cooling plate, heating plate, backingplate, electrode, etc.) is substantially reduced or eliminated, thelikelihood of arcing may also be reduced. That is, these fasteners mayno longer positioned near the pores or perforations of the electrodewhere arcing may be likely. Clamp ring fasteners, in contrast, tend lesslikely to arc, since they are generally positioned away from the poresor perforations of the electrode, and instead on the ground path. Aspreviously described, an arc is generally a high power density shortcircuit which has the effect of a miniature explosion that may result indamage to the substrate as well as the plasma chamber. Substantiallyreducing the number of metal fasteners may also reduce the likelihoodthat a secondary electrical discharge would occur as the rf electricalcharge is drained away. Furthermore, a dedicated return path may alsoinsure that the electrical characteristics of ground remain consistentbetween consecutive substrates or alternate plasma recipes.

Referring now to FIGS. 3A-D, a set of simplified diagrams of anelectrode assembly with a clamp ring, according to an embodiment of theinvention. FIG. 3A shows a lateral and isometric view of the electrodeassembly, according to an embodiment of the invention. Chamber lid 312is configured to mate with the plasma chamber in order to maintain asubstantial vacuum for plasma processing. In general, chamber lid 312comprises a top plate 312 b and circular stub 312 a that protrudes intothe plasma chamber (not shown) and provides a planar surface to which acooling plate 308 or heating plate 306 may be positioned. Circular stub312 a is further surrounded by a groove (defined by circular stub 312 aand top plate 312 b) into which gasket 314 is commonly placed.

In one configuration, cooling plate 308 is positioned below circularstub 312 a. Below to cooling plate 308 is generally heating plate 306which in combination allow the plasma gas temperature to be sustainedwithin recipe parameters in order to generally maintain etch quality andsubstrate yield. Below heating plate 306 is backing plate 304. Commonlymade of graphite, backing plate generally provides temperatureuniformity across electrode 302.

However, in contrast to commonly used configurations, clamp ring 301 issecured to electrode 302, forming a pocket or bucket into which coolingplate 308, heater plate 306, and backing plate 304 may be placed. Apocket configuration allows greater amount lateral and longitudinalplay, since metal fasteners are not needed to secure components (e.g.,cooling plate, heating plate, backing plate, etc.) within the pocket.Consequently, repetitive cycling of temperature may producesubstantially less stress and hence less damage the backing plate thanmore commonly used configurations. That is, the amount of contaminants(e.g., graphite particles, etc.) produced is minimized.

In an embodiment, clamp ring 301 may be secured to electrode 302 with aset of fasteners (e.g., bolts, screws, etc.). In an embodiment, clampring 301 and electrode 302 may be formed into a single unit. In anembodiment, the clamp ring 301 may be secured to electrode 302 in atongue and groove configuration. That is, a tongue in one componentextends into a groove in the other component. In an embodiment, clampring 301 may be welded to electrode 302. In an embodiment, clamp ring301 may be bonded to electrode 302. In an embodiment, clamp ring 301 hasa ledge that laterally extends towards the center of clamp ring 301,wherein electrode 302 sits on the lateral ledge.

FIG. 3D shows, in accordance with an embodiment of the invention, asimplified diagram of an electrode assembly with an electrode and aclamp ring forms into a single unit 350. As shown in FIG. 3D, clamp ring301 and electrode 302 may be formed into single unit 350.

Furthermore, reducing the number of fasteners also may make assembling,replacing, and/or installing the electrode assembly substantiallyeasier. As previously described, after the electrode assembly has beenrepeatedly exposed to plasma and/or temperature cycling, the actualtolerance may be reduced. However, substantially reducing or eliminatingmetal fasteners, and hence the corresponding required helicoils in thegraphite backing plate, may also reduce helicoil contamination andtolerance shrinkage within the fastener holes. In addition, sincetolerance shrinkage has been minimized, the likelihood of damage toelectrode components is also reduced. That is, the use of multiple tools(e.g., screwdriver, hammer, wedge, etc.) would not be required todislodge the components.

In addition, the electrode sub-assembly (e.g., electrode, backing plate,heater plate, cooling plate, clamp ring, etc.) may be pre-assembledprior to installation at the plasma processing system, potentiallyreducing the installation time and hence the period of time that theplasma chamber is offline. Furthermore, clamp ring 301 may function as adedicated rf return path along the outer surface of the electrodeassembly within the plasma chamber, minimizing the effect of a shiftingreturn path on the plasma load. As previously described, for a givenprocess recipe, it may be beneficial for the rf power delivery remainstable throughout the process to obtain a reliable process result.

Referring now to FIG. 3B, a more detailed lateral view of the electrodeassembly of FIG. 3A is shown, according to an embodiment of theinvention. In addition to previously described components, additionalelements are described. For example, between clamp ring 301 and backingplate 304, and between electrode 302 and clamp ring 301, a thermalinsulator may be used (e.g., vacuum, ceramic, silicone elastomer etc.).Electrically, thermal/electrical insulator 330 and 332 both helpelectrically isolate clamp ring 301 from the remainder of the electrodeassembly components, in order to get a clean and consistent rf returnpath as previously described. Thermally, thermal/electrical insulator330 and 332 both help attenuate the heat transfer from the plasmachamber to the inside of the electrode assembly, minimizing any thermalexpansion.

In contrast, a thermal/electrical conductive bond 336 may be usedbetween clamp ring 301 and cooling plate 308 for the opposite reason.That is, thermal/electrical conductive bond 336 electrically couplesclamp ring 301 to cooling plate 308 in order to complete the rf returnpath and insure an optimized ground. Thermally, thermal/electricalconductive bond 336 conducts heat from the plasma chamber, as well asthe electrode assembly to cooling plate 308. Consequently, the generatedheat may be removed from the electrode assembly by a fluid recalculatingthrough cavities in within cooling plate 308 to a chiller system.

Referring now to FIG. 3C, a simplified isometric view of the electrodeassembly of FIG. 3A is shown, in which the electrode assembly is beingattached to the chamber lid, according to an embodiment of theinvention. Unlike previous configurations, electrode sub-assemblycomponents (e.g., cooling plate, heater plate, backing plate, etc.) maybe quickly placed in a pocket formed by clamp ring 301 and electrode302, and then quickly attached to chamber lid 312, once chillerconnections (not shown) to cooling plate (not shown), and gasdistribution connections 342 to the electrode assembly, are aligned.

Referring now to FIG. 4A-C, a set of simplified diagrams of an electrodeassembly in which a clamp ring is integrated into the chamber lid,according to an embodiment of the invention. In this configuration, thechamber lid is comprises of two components: clamp ring/top plate 407 anda cover top plate 409. Clamp ring/top plate 407 is configured to form apocket in order to position the electrode sub-assembly components, aspreviously described, without having to further attach the sub-assemblyitself to the chamber lid. That is, the clamp ring is integrated intothe chamber lid. In addition, cover top plate 409 is configured tosecure, and hence compress, the sub-assembly components for plasmachamber operation, as well as to insure that proper chamber pressure ismaintained.

FIG. 4A shows a lateral and isometric view of the electrode assembly,according to an embodiment of the invention. In an embodiment, clampring/top plate 407 may be tiered or stepped to secure electrodecomponents (e.g., cooling plate 408, heater plate 406, backing plate404, electrode 402, etc.) without the use of metal fasteners. Inaddition, an annular overhang of the electrode 402 may sit on an annularledge of clamp 435, which annular ledge extends laterally toward thecenter to support the annular overhang of electrode 402.

Electrode sub-assembly components may then be compressed into the pocketby attaching cover top plate 409 to clamp ring/top plate 407. In anembodiment, cover top plate 409 is secured to clamp ring/top plate 407with a set of fasteners. In an embodiment, cover top plate 409 issecured to clamp ring/top plate 407 with a set of threads, such that itmay itself be torqued into clamp ring/top plate 407. As previouslydescribed, the pocket construction may allow a greater amount lateraland longitudinal play than in most commonly used configurations, sincemetal fasteners are not needed to secure electrode sub-assemblycomponents (e.g., cooling plate, heating plate, backing plate, etc.)within the pocket. Consequently, repetitive cycling of temperature mayproduce substantially less stress and hence less damage the backingplate than more commonly used configurations. That is, the amount ofcontaminants (e.g., graphite particles, etc.) produced is minimized.

Referring now to FIG. 4B, a more detailed lateral view of the electrodeassembly of FIG. 4A is shown, according to an embodiment of theinvention. In addition to previously described components, additionalelements are described. For example, an annular protecting shield 438 ispositioned, such that a lateral ledge extends toward the center andoverlaps the seam (as seen from below, i.e., from the plasma cloud)between the annular ledge of clamp ring/top plate 407 and electrode 402.This overlapping may shield the seam from plasma exposure, substantiallyreducing the amount of plasma species that may seep into the seam andpotentially damage components of the electrode assembly. In anembodiment, shield 438 comprises SiC or silicon carbide. In addition rfgasket 436 and o-ring seal may be placed between a top surface of clampring/top plate 407 and a bottom surface electrode 402 in order tooptimize the rf return path through clamp ring/top plate 407.

Referring now to FIG. 4C, a simplified isometric view of the electrodeassembly of FIG. 4A is shown, in which the electrode assembly is beingassembled, according to an embodiment of the invention. Unlike previousconfigurations, electrode sub-assembly components (e.g., cooling plate,heater plate, backing plate, etc.) may be quickly placed in a tiered orstepped pocket formed by clamp ring/top plate 407 once chillerconnections (not shown) to cooling plate 408, and gas distributionconnections (not shown) to the electrode assembly, are aligned.

While this invention has been described in terms of several preferredembodiments, there are alterations, permutations, and equivalents whichfall within the scope of this invention. For example, although thepresent invention has been described in connection with plasmaprocessing systems from Lam Research Corp. (e.g., Exelan™, Exelan™ HP,Exelan™ HPT, 2300, Versys™ Star, etc.), other plasma processing systemsmay be used (e.g., atmospheric plasma processing system, low-pressureplasma processing system, inductively coupled plasma processing system,capacitively coupled plasma processing system, etc.). In addition, theterm “above” as used herein does not require a direct contact betweenthe components disposed “above” one another. This invention may also beused with substrates of various diameters (e.g., 200 mm, 300 mm, etc.),as well as in systems in which the top electrode is powered.Furthermore, the term set as used herein includes one or more of thenamed element of the set. For example, a set of “X” refers to one ormore “X.”

Advantages of the invention include an apparatus for an optimized plasmachamber electrode. Additional advantages may include a consistent rfreturn path to ground, ease of manufacture, assembly, and installation,substantial reduction in the use of metal fasteners, reduction in thelikelihood of arcing, and the ability to preassemble the electrodesub-assembly prior to arrival at a plasma chamber.

Having disclosed exemplary embodiments and the best mode, modificationsand variations may be made to the disclosed embodiments while remainingwithin the subject and spirit of the invention as defined by thefollowing claims.

1. An electrode assembly configured to provide a ground path for aplasma processing chamber of a plasma processing system, said electrodeassembly comprising: an electrode configured to be exposed to a plasma;a heater plate disposed above said electrode, wherein said heater plateis configured to heat said electrode; a cooling plate disposed abovesaid heater plate, wherein said cooling plate is configured to cool saidelectrode; a plasma chamber lid configured to confine said plasma insaid plasma chamber, wherein said plasma chamber lid includes a ground;a clamp ring configured to secure said electrode to said plasma chamberlid, wherein said clamp ring and said electrode form a basket with atleast said heater plate being placed inside said basket such that saidclamp ring surrounds said heater plate, said basket is configured toallow longitudinal and lateral tolerances for thermal expansion of saidheater plate from repetitive thermal cycling, said clamp ring beingfurther configured to provide said ground path from said electrode tosaid chamber lid; and a shield shielding at least a portion of a bottomof said clamp ring, said portion of said bottom of said clamp ring beingdisposed between said shield and said electrode, said shield including aledge disposed under said portion of said bottom of said clamp ring,said portion of said clamp ring disposed under an outer annular portionof said electrode.
 2. The electrode assembly of claim 1, wherein saidclamp ring is disposed between said plasma chamber lid and saidelectrode.
 3. The electrode assembly of claim 1, further including abacking plate disposed between said electrode and said heater plate,wherein said backing plate is configured to substantially electricallyisolate said electrode from said heating plate.
 4. The electrodeassembly of claim 1, further including a first clamp ring electricalinsulator disposed between said clamp ring and said heater plate,wherein said first clamp ring electrical insulator is configured tosubstantially electrically isolate said clamp ring from said heaterplate.
 5. The electrode assembly of claim 1, further including a secondclamp ring electrical insulator disposed between said clamp ring andsaid cooling plate, wherein said second clamp ring electrical insulatoris configured to substantially electrically isolate said clamp ring fromsaid cooling plate.
 6. The electrode assembly of claim 1, wherein saidelectrode includes a showerhead.
 7. The electrode assembly of claim 1,wherein said electrode and said clamp ring are formed into a singleunit.
 8. The electrode assembly of claim 1, wherein said clamp ring isdisposed between said electrode and said cooling plate.
 9. The electrodeassembly of claim 1, wherein said clamp ring comprises aluminum.
 10. Theelectrode assembly of claim 1, further comprising an electrodesub-assembly, wherein said electrode sub-assembly includes at least saidelectrode, said heater plate, said cooling plate, said backing plate,and said clamp ring, and wherein said clamp ring is configured tofunction as a RF return path along an outer surface of said electrodesub-assembly within said plasma processing chamber.
 11. The electrodeassembly of claim 1, wherein said plasma processing system is one of anatmospheric plasma processing system, a low-pressure plasma processingsystem, an inductively coupled plasma processing system, and acapacitively coupled plasma processing system.
 12. An electrode assemblyconfigured to provide a ground path for a plasma processing chamber of aplasma processing system, said electrode assembly comprising: anelectrode configured to be exposed to a plasma; a set of componentsincluding at least a heater plate and a cooling plate; a plasma chamberlid configured to confine said plasma in said plasma chamber; a clampring configured to secure said electrode to said plasma chamber lid,wherein said clamp ring and said electrode form a basket with said setof components being placed inside said basket such that said clamp ringsurrounds said heater plate, said basket is configured to allowlongitudinal and lateral tolerances for thermal expansion of said set ofcomponents from repetitive thermal cycling, said clamp ring is furtherconfigured to provide said ground path from said electrode to saidchamber lid; and a shield shielding at least a portion of a bottom ofsaid clamp ring, said portion of said bottom of said clamp ring beingdisposed between said shield and said electrode, said shield including aledge disposed under said portion of said bottom of said clamp ring,said portion of said clamp ring disposed under an outer annular portionof said electrode.
 13. The electrode assembly of claim 12, wherein saidclamp ring is disposed between said plasma chamber lid and saidelectrode.
 14. The electrode assembly of claim 12, wherein saidelectrode includes a showerhead.
 15. The electrode assembly of claim 12,wherein said electrode and said clamp ring are formed into a singleunit.
 16. The electrode assembly of claim 12, wherein said clamp ringcomprises aluminum.
 17. The electrode assembly of claim 12, wherein saidplasma processing system is one of an atmospheric plasma processingsystem, a low-pressure plasma processing system, an inductively coupledplasma processing system, and a capacitively coupled plasma processingsystem.
 18. An electrode assembly configured to provide a ground pathfor a plasma processing chamber of a plasma processing system, saidelectrode assembly comprising: an electrode configured to be exposed toa plasma; a heater plate disposed above said electrode; a cooling platedisposed above said heater plate; a plasma chamber lid configured toconfine said plasma in said plasma chamber, said plasma chamber lidbeing further configured to form a basket with said electrode and toprovide said ground path, wherein said heater plate and said coolingplate are placed inside said basket such that said plasma chamber lidsurrounds said heater plate and said cooling plate, said basket isconfigured to allow longitudinal and lateral tolerances for thermalexpansion of said heater plate and said cooling plate from repetitivethermal cycling; and a shield shielding at least a portion of a bottomof said clamp ring, said portion of said bottom of said clamp ring beingdisposed between said shield and said electrode, said shield including aledge disposed under said portion of said bottom of said clamp ring,said portion of said clamp ring disposed under an outer annular portionof said electrode.
 19. The electrode assembly of claim 18, wherein saidheater plate is configured to heat said electrode.
 20. The electrodeassembly of claim 18, wherein said cooling plate is configured to coolsaid electrode.
 21. The electrode assembly of claim 18, wherein saidelectrode is one of a powered electrode and a grounded electrode. 22.The electrode assembly of claim 18, wherein said electrode includes ashowerhead.
 23. The electrode assembly of claim 18, wherein said plasmaprocessing system is one of an atmospheric plasma processing system, alow-pressure plasma processing system, an inductively coupled plasmaprocessing system, and a capacitively coupled plasma processing system.